with this patch everything works fine for me

draw.c

@@ -2,7 +2,6 @@
  * See LICENSE file for license details.
  */
 #include "dwm.h"
-#include <locale.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -167,16 +166,13 @@ getcolor(const char *colstr) {
 
 void
 setfont(const char *fontstr) {
-	char *def, *lc, **missing;
+	char *def, **missing;
 	int i, n;
 
-	lc = setlocale(LC_CTYPE, NULL);
-	setlocale(LC_CTYPE, "UTF-8");
 	missing = NULL;
 	if(dc.font.set)
 		XFreeFontSet(dpy, dc.font.set);
 	dc.font.set = XCreateFontSet(dpy, fontstr, &missing, &n, &def);
-	setlocale(LC_CTYPE, lc);
 	if(missing) {
 		while(n--)
 			fprintf(stderr, "missing fontset: %s\n", missing[n]);

main.c

@@ -4,6 +4,7 @@
 
 #include "dwm.h"
 #include <errno.h>
+#include <locale.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -240,6 +241,7 @@ main(int argc, char *argv[]) {
 	}
 	else if(argc != 1)
 		eprint("usage: dwm [-v]\n");
+	setlocale(LC_CTYPE, "");
 	dpy = XOpenDisplay(0);
 	if(!dpy)
 		eprint("dwm: cannot open display\n");